60,000 Oyster Cards Corrupted - Smart Card News

60,000 Oyster Cards Corrupted
By Dr David Everett, Smart Card & Identity News - July 08
What a month at Transport for London (TfL) who has experienced two major outages of
the Oyster card system. In the first system failure on the morning of Saturday 12th July
which lasted some 5 hours 60,000 cards were corrupted such that TfL had to issue 42,000
new cards holding the existing balances. The second shutdown on Friday 25th July
started at 5:30am and lasted several hours, on this occasion according to TfL there were
no corrupted cards (although some commuters were overcharged because they were
unable to check out) but the barriers had to be kept open during the morning rush hour.
TfL have been quick to blame Transys the Oyster Travelcard provider consortium that
includes EDS, Cubic Transportation Systems, Fujitsu Services Ltd and W. S. Atkins.
Apparently Transys had sent ‘incorrect data tables’ to the Oyster card readers at 275
underground stations (there are 287 in total).
TfL has a 17 year contract with Transys which was awarded in 1998 and commenced
operation in November 2002. The contract is worth £100m annually to Transys which
supplies, operates and markets the RFID ticket system. Apparently the contract has a
number of break clauses that allow for early termination and although Peter Hendry the
Transport Commissioner has been reported as enraged at the Oyster malfunctions any
such talk seems rather premature. It has been claimed that about 200,000 pay as you go
Oyster card users got a free ride on the second system failure for fares that would
normally incur costs from £1-50 for a single Zone 1 journey to £4-90 for a maximum
journey day cost. Given the time of day of the outage one suspects the direct lost revenue
to be no more than £500,000. Perhaps this can be covered by a few forfeited bonuses in
the Transys camp.

So what on earth is going on here? Two major outages within two weeks both due to the
transmission of ‘incorrect data tables’ to all the Oyster Card Terminals, is such an
accident possible or is there something more going on behind the scenes?
We have been reporting in SCN this year of the breaches in the security of the Mifare
chip which is the platform used by the Oyster card. In January we reported on the
discoveries of Karsten Nohl (University of Virginia) and Henryk Plötz who effectively
publically revealed much of the cryptographic architecture at the core of the Mifare chip.
In March we revealed the work of the digital security group at Radboud University in the
Netherlands who carried on with where Noel and Plotz left off. There can be no doubt
that both teams had cracked the Mifare Crypto-1 algorithms and last month we reported
on the Radboud team travelling the London Underground for free.
It gets worse because NXP (nee Philips Semiconductors) who own (Mifare is proprietary
technology) and manufacture the Mifare chips have now lost a ruling in the Netherlands
to block the Radboud University team from publishing their results. Mifare is now used
in up to a billion smart cards in mass transit and physical access control applications.
Nobody doubts that it will take years and significant costs to fix the problem which
means changing the cards, the smart card readers and some of the software middleware
that handles the application on the card. Involved in all of this is the cryptographic key
management, let nobody fool you, this needs to be changed as well.
If you were Transys the first thing you would try to do is to enhance the application
security around the use of the smart card. You can’t do anything about the cryptography
because that is deeply buried in the chips and can’t be changed (without changing the
chip). So the next best thing is to try and detect counterfeit cards or even authentic cards
where the data on the card has been manipulated. Can you imagine somebody selling a
kit for Oyster card users to reset the value on their cards, this is effectively what the
Radboud University team demonstrated in London.
So more about those ‘incorrect data tables’ what could that mean? Now as far as I know
the cost of the journeys on the London Underground have not changed for some time and
certainly not in the month of July so it’s not obvious that there would be any changes
here. But how about hot card lists? At the end of the day software on the Transys servers
could examine what the cards are up to, and notice everything seems to be linked to pay
as you go, which has a weaker registration system? If cards were being manipulated then
it should be possible to detect this back at base which should have a record of value loads
and spends. Each Mifare card has a unique (well its supposed to be although there have
been reports of duplicates) ID number which would be more difficult for the home user to
change although given the attacks reported previously any thing else relating to the
Oyster card application could be changed. With all this information Transys could send
out hot card lists to disable these suspect cards, this is what appeared to happen on the
first system failure. As an alternative you could just refuse access to the suspect cards on
the hot list and that perhaps is what happened on the latest system failure.

A much longer conversation is what do you do in such a situation? Conceptually there is
nothing new here, magnetic stripe bank cards were around for years, long after it was
widely reported on how easy it was (complete with instructions) to create counterfeit
cards. It’s all about risk management and most important the stakeholders, who actually
loses money (and/or credibility) when the system is attacked?
Rumours abound that ITSO has produced a migration strategy from the use of Mifare
cards to another approved Customer Media. At first sight that would appear to provide
two options or three if you count the new NXP Mifare Plus chip yet to be released. That
would mean the NXP DESFire or the general purpose CPU card with an ISO 7816-4 file
structure configured as an ITSO structure. Given the opportunity which way wouldn’t
you go? Watch this space for more news on DESFire.
According to the Transys website the ‘Oyster’ brand was adopted as a name representing
security and value coming from the concepts of the oyster shell and pearl, I expect right
now they might want to eat their words. Thinking of food I wonder if the Octopus card in
Hong Kong has similar problems?
David Everett